The purpose of this study was to understand the power、boundary and alliance between grandparents and parents when they want to decide who´s going to nurture the new born baby. The participants were two pairs of mother in-law and daughter in-law, and one pair of mother and daughter. In-depth interview was adopted to collect data, and data was analyzed from the opinion of structural family therapy. The main findings were as follows: (1) The first generation have more vantage, and mother in-law is the most powerful person to make the decision, however the second generation was not totally passive. (2) Parents weren´t both responsible for nurturing the baby, and such a situation strengthen grandmother´s duty to take care of grandchildren. Even the social culture give the mother in-law some duty, therefore a capable grandmother would take care of grandchildren, and she wouldn´t say NO. (3) Men who were more passive than women who were expected to have more responsibility for taking care of children. The woman of second generation was more active than the first generation to let spouse make the decision together. (4) Daughter in-law pay more attention to the paternal priority belonging to the culture. The effect of culture is more powerful then personal expectancy. Daughter in-law would think about mother in-law´s opinion first. Thus, if mother and daughter could cooperate again, the boundary between them would be more diffuse than that between mother in-law and daughter in-law. (5) The interaction between two generations would be connected and maintained by the closed family member, here fore, the way of interaction would be continued in the original way. (6) In the second generation, the spouse alliance was a stable subsystem. The original parental alliance, especially mother and son, would be kept, but it´s not necessary to influence the working of the second generation. If parental alliance or spouse alliance were not stable in their relationship, each member, especially daughter in-law, would worry that her own alliance would be threatened by the other alliance. Base on the results, discussion and suggestion were presented.